相关论文: Prospects and Limitations for Constraining Light R…
Thermal freeze-out is a prominent example of dark matter (DM) production mechanism in the early Universe that can yield the correct relic density of stable weakly interacting massive particles (WIMPs). At the other end of the mass scale,…
The existence of dark radiation that is completely decoupled from the standard model in the early Universe leaves open the possibility of an associated dark radiation isocurvature mode. We show that the presence of dark radiation…
In the standard hot big bang model, the expansion of the early universe is given by the Friedmann equation with an energy density dominated by relativistic particles. Since in a variety of models this equation is altered, we introduce…
We find new and universal relations for the properties of dark matter particles consistent with standard relic abundances. Analysis is based on first characterizing the $s$-channel resonant annihilation process in great detail, keeping…
We discuss the effects of a possible time variation of the Newton constant $G_{\rm N}$ on light elements production in Big Bang Nucleosyntesis (BBN). We provide analytical estimates for the dependence of primordial abundances on the value…
Almost every helium atom in the Universe was created just a few minutes after the Big Bang through a process commonly referred to as Big Bang Nucleosynthesis. The amount of helium that was made during Big Bang Nucleosynthesis is determined…
The standard theoretical estimation of the thermal dark matter abundance may be significantly altered if properties of dark matter particles in the early universe and at the present cosmological epoch differ. This may happen if, e.g., a…
We investigate scenarios in which a charged, long-lived scalar particle decouples from the primordial plasma in the Early Universe. We compute the number density at time of freeze-out considering both the cases of abelian and non-abelian…
The effects of magnetic fields on Big Bang Nucleosynthesis(BBN) have been calculated, and the impact on the abundances of the light elements have been investigated numerically. An upper limit on the strength of primordial magnetic fields…
The apparent discrepancy between abundances of light nuclides predicted by the standard Big-Bang and observational data is explained, by assuming the presence of metastable H dibaryons at the nucleosynthesis era. These dibaryons could be…
Oscillations between ordinary and sterile neutrinos can generate large neutrino asymmetries in the early universe. These asymmetries can significantly affect big bang nucleosynthesis (BBN) through modification of nuclear reaction rates. We…
According to the standard models of particle physics and cosmology, there should be a background of cosmic neutrinos in the present Universe, similar to the cosmic microwave photon background. The weakness of the weak interactions renders…
We consider the cosmological effects of sterile neutrinos with the masses of $150- 450$ MeV. The decay of sterile neutrinos changes the thermal history of the Universe and affects the energy density of radiation at the recombination and the…
Scalar-tensor theories of gravity provide a consistent framework to accommodate an ultra-light quintessence scalar field. While the equivalence principle is respected by construction, deviations from General Relativity and standard…
The relic abundance of asymmetric Dark Matter particles in the scalar--tensor model is analysized in this article. We extend the numeric and analytic calculation of the relic density of the asymmetric Dark Matter in the standard…
From the observations of the anisotropies of the Cosmic Microwave Background (CMB) radiation, the WMAP satellite has provided a determination of the baryonic density of the Universe, \Omega_b.h^2, with an unprecedented precision. This…
A new upper limit on the amplitude of primordial magnetic field (PMF) is derived by a comparison between a calculation of elemental abundances in big bang nucleosynthesis (BBN) model and the latest observational constraints on the…
We consider the stochastic background of gravitational waves produced during the radiation-dominated hot big bang as a constraint on the primordial density perturbation on comoving length scales much smaller than those directly probed by…
The primordial deuterium abundance probes fundamental physics during the Big Bang Nucleosynthesis and can be used to infer cosmological parameters. Observationally, the abundance can be measured using absorbing clouds along the lines of…
The origin of dark matter as a thermal relic offers a compelling way in which the early universe was initially populated by dark matter. Alternative explanations typically appear exotic compared to the simplicity of thermal production.…